1. Field of the Invention
The present invention relates to a substrate processing apparatus that performs a predetermined substrate process such as cleaning process by supplying a processing liquid to a semiconductor substrate, glass substrate for liquid crystal display, glass substrate for photomask, substrate for optical disk or the like (hereinafter referred to simply as a “substrate”), while rotating the substrate.
2. Description of the Background Art
There has conventionally been used a substrate processing apparatus of single-wafer type that performs etching and cleaning processes by supping a chemical solution or rinsing pure water (chemical solution and pure water are generally called “processing liquid” in the present specification) to the surface and/or reverse of a substrate mounted on a spin base, while rotating the substrate. The substrate processing apparatus of this type is usually provided with a cup unit for receiving and recovering a processing liquid flying spattering from the substrate in rotation.
As a cup unit to recover processing liquid, there has been used one in which a plurality of cups are so arranged in multistage as to separately recover various types of processing liquids and then separate depending on the purpose of recovery. For example, the individual processing liquids are separately and properly recovered by changing the type of cup disposed about the periphery of the substrate, depending on the type of processing liquid.
However, since a plurality of different cylindrical cups are coaxially arranged in the conventional cup unit, a cup disposed closer to the axis has a smaller internal diameter. Particularly, the upper end part of each cup is inwardly inclined (toward the substrate held by the spin base), so that the upper internal diameter of the innermost cup is further reduced.
This causes the problem that the peripheral part of the substrate held by the spin base is considerably close to the upper part of the innermost cup and the processing liquid flying spattering from the substrate in rotation strikes the cups and it becomes fine droplets to be attached on the substrate surface. There is also the possibility that the processing liquid so adhered to the substrate is then dried to form particles contaminating the substrate.